WO2006110481 <<Production of polycrystalline silicon>> discloses the method wherein polysilicon is suggested to deposit onto hollow bodies. The hollow bodies replace slim rods in a conventional Siemens-type reactor and may be heated internally by resistance elements. The diameter of hollow bodies is selected to provide the deposition surface area much larger than that of silicon slim rods.
However, the profitability of this method is reduced by use of the additional expensive equipment and complicated electrical systems. Besides, the productivity of this method cannot be considerably increased since the deposition occurs from the gas mixture, which is the same as that leaving the reactor.
A method of polycrystalline silicon production from a gas phase is also known (U.S. Pat. No. 6,544,333, filling date Apr. 24, 2001, publication date Feb. 7, 2002 <<Chemical vapor deposition system for polycrystalline rod production>>), which comprises supply of a silicon-bearing gas through a system of pipes into the reactor, where silicon is deposited on surfaces heated by induction coils with production of output gases.
Such method of rod heating allows increasing the rod surface temperature, final rod diameter, and, thereby, the productivity becomes higher. However, the required apparatus and its electrical system are extremely complicated and expensive.
Both these methods have one common important disadvantage: the input gas is mixed with the products of silicon deposition reactions in the reactor vessel and silicon deposits from depleted mixture as compared with the supplied gas. Silicon grows from the mixture being the product of the process, and, hence, the reactor characteristics such as productivity, energy consumption, and gas-to-silicon conversion become worse.